SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '821f125540e967dc7e9d79a0dcf3976ea3b7462113924dd6bf820ccfb719a9cf' 
  AND token = 'dwz3V+3OB7pjVkRcBzqu0mCTUO+Yb/l4LEudIMkBAwU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}